display raw clipping

[Beep6581]

Originally reported on Google Code with ID 988

This is an enhancement suggestion.

RawTherapee development version 4.0.2.26

There is now a RAW histogram, which is great.

What's still missing (I think) is the possibility to display highlight clipping in
the preview window. It would be great if you enable the RAW histogram that the highlight
warning would change to display the RAW clipping (if any) instead.

Preferably, the clipping shades would indicate which/how many channels that are clipped.
White if all channels are clipped, a bit darker if 2 of 3 and even darker if only 1.
Another alternative is tohave the color of the actual channels clipped, white if all,
green if only green, green+blue=cyan if both green and blue etc.

Reported by torger@ludd.ltu.se on 2011-09-11 08:06:22

[Beep6581]

Can you exemplify the use of this raw clipping indicator in the preview?

Reported by entertheyoni on 2011-09-11 22:08:34

[Beep6581]

One could say that it is the same use as the RAW histogram, to be able to verify how
well exposed the RAW file is. Still life photographers often do "Expose To The Right",
that is try to expose as far right as possible without overexposing. The purpose is
to capture as many photons as possible which increases dynamic range, important in
for example landscape photography.

Unfortunately most cameras don't have built-in RAW histograms and clip highlighting
so there is some guesswork. One popular method is to bracket, that is take several
exposures (often possible in still life photography, since the scene is, well, still)
and then in post-processing take the one that is most to the right but does not overexpose
anything important.

The RAW histogram is helpful to identify this, but it would be even further helpful
with this clipping highlighting, because in some cases you can accept overexposure
if it is in unimportant areas, or say if only 2 channels are blown and the highlight
is white (common for clouds).

Reported by torger@ludd.ltu.se on 2011-09-12 06:35:59

[Beep6581]

I once tried to extend our indicator for RAW (and LCMS) clippings, but it’s not that
easy.

For one the image goes through some transformations like distortions, so you cannot
simply store a clipping array at RAW/LCMS level, it need to be transformed in parallel,
too. Would be easier after an RT rewrite.

Second is that the RAW clipping is sometimes fuzzy, depending on color channel it is
not always a clean maximum peak like one would expect, and in those cases you can have
many discuss what should be considered clipped ;-)

A poor man’s solution would be to include the clipping in the image, but it would be
slow and the clipping indicators would not be clean white/black but change colors and
cause e.g. sharpening artifacts depending on the other image control.

Reported by oduis@hotmail.com on 2011-09-12 08:06:44

[Beep6581]

It is not exactly a critical feature, so if it is difficult to implement it's better
to focus on more important stuff for now. Could be kept on the "nice to have" list
for the future.

Reported by torger@ludd.ltu.se on 2011-09-12 08:15:04

[Beep6581]

Reported by entertheyoni on 2011-09-12 10:03:18

• Labels added: Type-Enhancement, Component-UI
• Labels removed: Type-Defect

[Beep6581]

Reported by torger@ludd.ltu.se on 2013-10-24 18:19:49